The use of electromagnetic forces for this purposes is well known and has been described in numerous patents relating to electromagnetic pumps, which patents may be classified into two broad categories.
The first category concerns pumps for liquid sodium and is mostly concerned with fast neutron nuclear reactors. Most of the electromagnetic pump patents which we have come across worldwide relate to this type of pump. The earliest patents of which we are aware date from the beginning of this century and the first pump was constructed by Hartman in 1918. The main patents are in the names of Albert Einstein and Leo Szelard and were originally filed in Berlin in the 30s (e.g. German patent No. 555.413 Class 17a group 304 and patent No. 476.812 Class 31c group 26). The sodium is kept out of contact with the air in ducting which is generally made of low carbon stainless steel, and the active portion of the pump is constructed around the ducting such that the magnetic portion and the electrical windings are themselves in air.
These "sodium" pumps are mentioned here by way of background since their construction and use are very different from those of the present application, although the same physical principles are used to cause the metal to move, which means, inter alia, that a pump in accordance with the present invention is perfectly capable of being used for pumping liquid sodium.
The second category of electromagnetic pump is used industrially for moving molten metals other than sodium. Such pumps are used in foundry technology rather than in nuclear reactor technology. Generally speaking, the electromagnetic pumps used in foundries operate on one of the following three principles:
(1) Pumps operating on Lenz's law; PA1 (2) Submerged pumps; and PA1 (3) Pumping systems which are mounted directly on a furnace but which are outside the furnace.
A common drawback with all of these pumps is that they cause molten metal to flow through ducting which is external to the furnace in which the metal is melted. As a result, there is a high risk of the electrical portions and any surrounding equipment of the pump being destroyed in the event of accidental leakage of molten metal.
Preferred embodiments of the present invention reduce the danger of the pump being damaged by the liquid metal.